1. Field of the Invention
This invention relates to a positioning stage apparatus for use in a semiconductor exposure apparatus, a precision machine tool, a precision measuring machine or the like, and an exposure apparatus using the same.
2. Related Background Art
In a semiconductor exposure apparatus, a precision machine tool, a precision measuring machine, etc., it is required to highly accurately position a substrate such as a wafer to be exposed, a workpiece or an object to be measured. For this purpose, there has been developed a positioning stage apparatus in which a holding board for holding a substrate or a workpiece is kept in non-contact with a guide surface for guiding it by a hydrostatic bearing device and a linear motor is used as a driving device for moving the holding board, whereby the accuracy and speed of positioning are improved. An example of such a positioning stage apparatus according to the prior art is shown in FIG. 15 of the accompanying drawings.
The positioning stage apparatus E.sub.0 of FIG. 15 is a vertical type positioning stage apparatus for use in an X-ray exposure apparatus using X-rays such as synchrotron radiation as exposure light, and comprises an x stage 102 guided by an x guide 102a integral with a base 101 and reciprocally movable in one direction in a horizontal plane (hereinafter referred to as "x-direction"), a y stage 103 guided by a y guide 103a integral with the x stage 102 and reciprocally movable in a vertical direction (hereinafter referred to as "y-direction"), a wafer chuck 104 provided on the y stage 103, an x electric cylinder 105 for moving the x stage in x-direction, an x linear motor 106 for moving the x stage 102 by a minute amount in x-direction, a y electric cylinder 107 for moving the y stage 103 in y-direction, a y linear motor 108 for moving the y stage 103 by a minute amount in y-direction, and a constant tension spring 109 for offsetting the weight of the y stage 103 by the tension thereof. The rod 105a of the x electric cylinder 105 is connected to the x stage 102 through an x gap joint 105b, and the rod 107a of the y electric cylinder 107 is connected to the y stage 103 through a y gap joint 107b.
The x gap joint 105b comprises a striking plate 105c provided integrally on the free end of the rod 105a of the x electric cylinder 105, and a pair of L-shaped members 105d protruding from a side of the x stage 102. The striking plate 105c is loosely fitted in a gap formed between the side of the x stage 102 and the restraining portion 105e of each L-shaped member 105d opposed thereto, and the dimension of said gap is several microns to several tens of microns. When the rod 105a of the x electric cylinder 105 moves forward in response to a command signal from a command line, not shown, the striking plate 105c bears against the x stage 102 and moves it forward, and when the rod 105a of the x electric cylinder 105 moves backward, the striking plate 105c comes into engagement with the restraining portion 105e of each L-shaped member 105d and retracts the x stage 102. Thereby, the x stage 102 is moved to several microns short of an x-direction command position based on the aforementioned command signal. The y gap joint 107b is likewise constructed.
The x linear motor 106 comprises a stator 106a integral with the base 101 and a small mover 106b integral with the x stage 102, and the y linear motor 108 likewise comprises a stator 108a integral with the x stage 102 and a small mover 108b integral with the y stage 103. Each of the stators 106a and 108a, as shown in FIG. 16 of the accompanying drawings, comprises a number of coils C.sub.0 held on a long coil holding member H.sub.0, and produces a thrust in each of the movers 106b and 108b by a change in magnetic field when an electric current is supplied to each coil C.sub.0, and as previously described, the x stage 102 and the y stage 103 are moved by the driving of the x electric cylinder 105 and the y electric cylinder 107, and each of the stators is provided with a current switching device for detecting the new position of each mover 106b, 108b and supplying an electric current to a predetermined coil when each mover 106b, 108b moves with the x stage or the y stage.
The wafer chuck 104 has a vertical adsorbing surface 104a which adsorbs a wafer W.sub.0 by its vacuum adsorbing force. The position of the wafer chuck 104 in the x-direction is monitored by an x interferometer which receives reflected light from an x mirror, not shown, provided on the y stage 103, and the output thereof is negatively fed back to an x servo calculator, not shown, which drives the x linear motor 106 on the basis of the difference between the command signal transmitted from the command line and the output of the x interferometer to thereby move the x stage 102 by a minute amount. Also, the position of the wafer chuck 104 in the y-direction is monitored by a y interferometer, not shown, which receives reflected light from a y mirror provided on the y stage 103, and the output thereof is negatively fed back to a y servo calculator, not shown, which drives the y linear motor 108 to thereby move the y stage 103 by a minute amount. Such fine movement adjustment by the x linear motor 106 and y linear motor 108 is effected after as previously described, the x stage 102 and y stage 103 are moved to several microns short of the command positions based on the respective command signals by the x electric cylinder 105 and y electric cylinder 107, respectively, whereby the y stage 103 is finally positioned.
Each of the x electric cylinder 105 and y electric cylinder 107, as shown in FIG. 17 of the accompanying drawings, comprises a motor M with a water jacket, a gear train G, a screw rod R rotatably supported by a bearing B, and a nut N axially moved by the screw rod R. The nut N is provided integrally with the rod 105a and 107a of the x electric cylinder 105 and the y electric cylinder 107, respectively, and the rotation of the motor M is transmitted to the screw rod R through the gear train G so that the nut N may be moved forward and backward by the rotation of the screw rod R. The motor M has a water jacket as previously described and therefore, there is no possibility of the temperature of the x stage 102 and y stage 103 rising due to the heating of the motor. Also, the x linear motor 106 and y linear motor 108 are used only for positioning servo and do not effect the acceleration and deceleration of the stages, and therefore the amount of heat generated therein is very small and compact design is possible as previously described. The positioning stage apparatus E.sub.0 thus prevents the reduction in the accuracy of positioning caused by the heating of the driving devices for the x stage 102 and y stage 103 to the utmost and also realizes the highly accurate and highly responsive positioning by the linear motors.